A capacitance video disc system has been described by Clemens in U.S. Pat. No. 3,842,194. The disc described comprises a plastic disc containing an information track having audio, video and color information in the form of a surface relief pattern arranged in the surface of the disc which can be played back with a stylus. The video disc of Clemens had a conductive metal coating to provide the conductivity required for capacitive pickup and a thin layer of a dielectric material thereover. An electrode on the playback stylus completed the capacitor.
Improvements have been made in this system whereby the disc is made from a conductive plastic material, as disclosed by Fox et al. in copending application Ser. No. 105,550 filed Dec. 20, 1979, which is a continuation of application Ser. No. 818,279 filed July 25, 1977, now abandoned. A polyvinylchloride based molding composition is mixed with sufficient amounts of finely divided carbon black particles so that the resulting composition has the conductivity required for capacitive playback. A thin layer of the polyvinylchloride surrounds each of the conductive carbon particles so that a thin dielectric layer is present at the surface.
The use of a conductive plastic eliminates the need for separate metal and dielectric layers on the disc surface and thus has simplified manufacture of the disc. However, we have found the stability of these discs with respect to environmental fluctuations of temperature and relative humidity has been less than satisfactory. Discs which on initial playback have excellent playback characteristics deteriorate with respect to playback after storage under ambient conditions. This deterioration is particularly marked when the discs are exposed to high temperature and/or high relative humidity conditions.
Huck et al. in a copending application Ser. No. 091,878 filed Nov. 7, 1979 and entitled "VIDEO DISC PROCESSING," have disclosed that video discs that have been cleaned by washing or spraying with an aqueous solution have improved stability. This copending application is incorporated herein by reference. The preferred solution is one made up of a 5 percent solution of a mixture of organic alcohols commercially available as 1160B Conditioner from the Shipley Company which contains as its principal ingredients about 96.2 mol percent of Lubrol, which has the formula ##STR1## about 3.8 mol percent of 1,2-propanediol and a minor amount of triisopropanol amine. The discs are sprayed or immersed in this solution and thereafter rinsed with water to remove the conditioner.
Over time, additional materials appear to come to the surface of the video disc, and the above cleaning procedure has been found to be less than satisfactory insofar as long term stability after exposure to high temperature and high relative humidity is concerned. Thus an improved cleaning process has been sought to reduce this problem, which has been referred to as carrier distress.